Question

1. when someone gets hurt playing sports, often times a cold pack is used for the injury. the cold pack takes up more energy than it gives off and it gets very ______ to the touch. this means that the reaction taking place is endothermic or exothermic
2. how do you know baking a cake is a chemical reaction?
3. there are ______ naturally occurring elements.
4. if elements are in the same group on the periodic table, what does that tell you?

true or false

1. when something burns, heat & light are given off. t or f
2. your stomach growling is an example of a chemical reaction. t or f
3. water is 1 part hydrogen and 2 parts oxygen. t or f
4. when baking a cake, a chemical reaction takes place. t or f
5. everything is made of chemicals. t or f
6. alfred nobel invented dynamite. t or f
7. you should always wear safety goggles when working with chemicals. t or f
8. sodium chloride is better known as sugar. t or f
9. a substance can feel a little warm if the reaction is endothermic. t or f
10. when developing film, red light doesnt affect the picture. t or f
11. a cold pack gets cold because the reaction takes more energy than it gives off. t or f
12. if chemicals behave similarly, they are grouped together on the periodic table. t or f
13. chemical reactions happen when protons link atoms together. t or f
14. when vinegar and baking soda react, oxygen is produced. t or f
15. fireworks are not an example of chemical reactions. t or f

Explanation:

1. Combustion (burning) is an exothermic reaction that releases heat and light.
2. Stomach growling is a mechanical process (peristalsis) in the digestive system, not a chemical reaction.
3. Water's chemical formula is \(H_2O\), which means 2 parts hydrogen and 1 part oxygen.
4. Baking a cake involves chemical reactions like the decomposition of baking powder (\(2NaHCO_3

ightarrow Na_2CO_3 + H_2O+CO_2\)) and protein denaturation.

1. Everything in the universe is made of atoms and molecules (chemicals).
2. Alfred Nobel is credited with inventing dynamite.
3. Safety goggles protect the eyes from chemical splashes.
4. Sodium chloride (\(NaCl\)) is table - salt, while sugar is \(C_{12}H_{22}O_{11}\).
5. Endothermic reactions absorb heat, so the substance would feel cold, not warm.
6. Red light has a longer wavelength and lower energy, so it doesn't expose photographic film as much as other lights.
7. Cold packs use endothermic reactions (e.g., \(NH_4NO_3 + H_2O

ightarrow NH_4^+(aq)+NO_3^-(aq)\)) that absorb heat.

1. The periodic table groups elements with similar chemical properties (e.g., alkali metals in Group 1).
2. Chemical reactions involve the rearrangement of electrons (forming and breaking bonds), not protons.
3. When vinegar (\(CH_3COOH\)) and baking soda (\(NaHCO_3\)) react, \(CO_2\) is produced (\(CH_3COOH + NaHCO_3

ightarrow CH_3COONa + H_2O + CO_2\)).

1. Fireworks involve chemical reactions (e.g., combustion of fuels and decomposition of metal salts for color).

Answer:

1. T
2. F
3. F
4. T
5. T
6. T
7. T
8. F
9. F
10. T
11. T
12. T
13. F
14. F
15. F