Question

a block of wood has a mass of 500 g and a volume of 100 cm³. a piece of metal has a mass of 1000 g and a volume of 100 cm³. which object has a higher density? a. the block of wood b. the piece of metal c. they both have the same density. which of these materials is most likely to float when placed in water? a. wood b. gold c. aluminum d. iron sarah has a mixture of sand and iron filings. which tool can she use to separate the iron filings from the sand? a. sieves b. filters c. magnets what happens to the volume of 50 ml of orange juice when 50 ml of sugar is dissolved in it? a. the volume becomes larger. b. the volume becomes smaller. c. the volume stays about the same. which scientists work on radiation led to new cancer treatments? a. robert boyle b. dmitri mendeleev c. marie curie d. linus pauling

Explanation:

1. Calculate densities

• Formula: Density \(d=\frac{m}{V}\)
• For wood: \(m = 500g\), \(V=100cm^{3}\), so \(d_{wood}=\frac{500g}{100cm^{3}} = 5g/cm^{3}\)
• For metal: \(m = 1000g\), \(V = 100cm^{3}\), so \(d_{metal}=\frac{1000g}{100cm^{3}}=10g/cm^{3}\)

2. Compare densities

Since \(d_{metal}>d_{wood}\), the metal has a higher density.

3. Floating principle

Objects with density less than water (\(1g/cm^{3}\)) float. Wood has density around \(0.5 - 1g/cm^{3}\) (varies by type), while gold (\(\approx19.3g/cm^{3}\)), aluminum (\(\approx2.7g/cm^{3}\)), and iron (\(\approx7.87g/cm^{3}\)) have higher densities than water.

4. Separation principle

Iron is magnetic. Magnets can attract iron filings, while sand is non - magnetic. Sieves and filters separate based on particle size (not applicable here as both sand and iron filings can be of similar small sizes).

5. Volume change in solution

When sugar dissolves in orange juice (a liquid), the sugar molecules fit into the spaces between the juice molecules. The volume change is negligible compared to the sum of the two volumes (\(50 + 50\)), so the volume stays about the same.

6. Scientist's contribution

Marie Curie worked on radioactivity. Robert Boyle is known for Boyle's law (\(PV = constant\) for ideal gases at constant temperature). Dmitri Mendeleev created the periodic table. Linus Pauling worked on chemical bonding and protein structures.

Answer:

1. B. the piece of metal
2. A. wood
3. C. magnets
4. C. The volume stays about the same.
5. C. Marie Curie