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2. intermediate information about substances w, x, y and z is shown in …

Question

  1. intermediate information about substances w, x, y and z is shown in the table below. substance | appearance | what happens when heated | what happens when added to water | additional information w | grey solid | reacts with oxygen in the air to form a white solid | insoluble in water | consists of only one type of atom, and green and substances can have proportions x | white powder with green speckles | turns green, then blue, different substances has a thin film. the white powder remains white. | the green substance is insoluble. the white powder dissolves to form a colourless solution. | the white and green substances can have proportions y | blue crystals | breaks down to form a white powder | dissolves to form a blue solution | consists of more than one type of atom. cannot be broken down into simpler substances z | yellow powder | melts to form a yellow liquid | insoluble in water | broken down into simpler substances (a) using the information provided, put a tick (✓) in each row to indicate whether each of the substances w, x, y and z is an element, a compound or a mixture. substance | element | compound | mixture w | ✓ | | x | | ✓ | y | ✓ | | z | | ✓ | (b) state two physical changes from the information given in the table. 1 2 (c) state two chemical changes from the information given in the table. 1 2

Explanation:

Brief Explanations

To determine physical changes, we look for changes in appearance or state without new substances. For W: reacting with oxygen (but wait, no—wait, physical changes are like state changes, dissolving? Wait, no, the table for W: appearance grey solid, when heated reacts with oxygen (chemical), but physical changes: maybe melting? Wait, no, the table's "What happens when heated" for X: turns green, then black (chemical). For Y: breaks down (chemical). Wait, the physical changes: let's check the table again. Wait, the question (b) is state two physical changes. Let's see:

  1. Substance Y: breaks down? No, that's chemical. Wait, maybe W: when heated, is it a physical change? Wait, no, the "What happens when heated" for W: reacts with oxygen (chemical). Wait, maybe the "Appearance" and "What happens when added to water" or "Melting"? Wait, maybe Substance Z: melts to form a yellow liquid (physical change, state change from solid to liquid). Substance Y: breaks down? No. Wait, maybe Substance X: the white powder with green crystals—maybe dissolving? No, X is insoluble. Wait, maybe the physical changes are:
  1. Substance Z melting (solid to liquid, physical, no new substance).
  2. Substance Y breaking into powder? Wait, no, breaking down is chemical. Wait, maybe Substance W: is a grey solid, maybe grinding? No. Wait, the table for Z: "Melts (to form a yellow liquid)"—that's a physical change (state change, melting). For Y: "Breaks down to form a white powder"—no, that's chemical. Wait, maybe Substance X: the green crystals and white powder—maybe mixing? No. Wait, maybe the two physical changes are:
  1. Substance Z melting (solid to liquid, physical change as it's a state change without new substance).
  2. Substance Y being broken into powder (physical change, size change, no new substance—if "breaks down" here means physical breaking, not chemical decomposition). Wait, the table says "Breaks down to form a white powder"—no, that's chemical. Wait, maybe I misread. Let's re-express:

Physical changes are changes in state, shape, size, dissolving (if no new substance). Let's check each substance:

  • W: grey solid, reacts with oxygen (chemical), insoluble in water.
  • X: white powder with green crystals, when heated turns green then black (chemical), insoluble in water.
  • Y: blue crystals, when heated breaks down to white powder (chemical), dissolves in water (physical, dissolving is physical if no reaction—wait, Y dissolves to form blue solution, so dissolving Y is a physical change (state from solid to solution, no new substance).
  • Z: yellow powder, melts to yellow liquid (physical, melting, state change).

So two physical changes:

  1. Substance Y dissolving in water to form a blue solution (physical, dissolving, no new substance).
  2. Substance Z melting to form a yellow liquid (physical, state change from solid to liquid).

Wait, but the question (b) is "State two physical changes from the information given in the table." So:

  1. Substance Z melts (changes from solid yellow powder to liquid yellow, physical change, state change).
  2. Substance Y dissolves in water to form a blue solution (physical change, dissolving, no new substance formed).

Alternatively, Substance Y breaking into powder? Wait, the table says "Breaks down to form a white powder"—that's chemical (decomposition). So better to use Z's melting and Y's dissolving.

For (g), chemical changes:

  1. Substance W reacting with oxygen (forms a new substance, chemical change).
  2. Substance X reacting when heated (turns green then black, new substances, chemical change).
  3. Substance Y brea…

Answer:

(b) 1. Substance Z melts to form a yellow liquid (physical change, state change from solid to liquid).

  1. Substance Y dissolves in water to form a blue solution (physical change, dissolving without new substance).

(g) 1. Substance W reacts with oxygen (chemical change, new substance formed).

  1. Substance Y breaks down (chemical change, decomposition into new substance).