creating salt by reacting sodium metal and chlorine gas
1. Which of the following procedures involves a physical change in one of the substances?
separating an oil from solution by cooling it: physical
(* creating salt by reacting sodium metal and chlorine gas: chemical; allowing a nail to rust: chemical; building a model rocket propelled by mixing baking soda and vinegar: chemical)
2. Which of the following is a homogenous mixture of two or more pure substances?
(* they are all homogeneous, but only alcohol is made up of pure substances)
3. A container has the dimensions of 30 cm x 50 mm x 0.2 m. The density of its contents is 2.5 g/cm3. What is the mass of the substance in kilograms? (D = m/V)
(* M = 3,000 (2.5) = 7,500 g = 7.5 kg)
4. A chemical reaction gives off 2,100 kJ of heat energy. About how many calories is this? (1 calorie = 4.18 Joules)
5.0 x 10^5 calories
(* kilojoule (kJ), an SI unit of energy equal to 10^3 joules; 2100 / 4.18 = 502.392344 and then move the decimal point 2 times to the left. That is another 10^2 so 10^3 + 10^2 = 10^5)
5. A material has a density of 8.9 g/cm3. You have 3 cm^3 of the substance. What is the material’s mass in grams?
(* M = 3(8.9) = 26.7 g; when rounded is 27 g)
1. allowing oil to seperate is a physical change. The oil didn’t turn into anything else by reacting
2. alcohol is homogeneous. Alcohol and water, they are misscible (not sure of the spelling)
3. none of those are true. A kilojoule is 1000 joules. all of the values you gave were under 2215.4 joules In other words they were all under 2.215 kilojoules
But of course if you mean 2.1 kilojoules and had a typing mistake then the answer is 5.0 x 103 calories
4. The material’s mass should be actually 26.7 grams but according to the values you gave it would be closest to 27 grams
i could say chemical exchange. A *chemical exchange* is a technique wherein reactants are replaced right into a variety of of distinctive products. A chemical exchange happens on each and every occasion new compounds are formed or present compounds decomposed. in this reaction, chemical bonds between atoms are broken and new chemical bonds formed. This leads to a rearrangement of the chemical bonds. There are various categories of chemical exchange. those contain synthesis, decomposition, single displacement, double displacement, neutralization, precipitation and redox. alerts of a chemical exchange contain a *shade exchange*, the formation of a precipitate, the formation of gas, production of warmth or easy, the visual appeal of a sparkling substance, a use-up of a beginning substance or a transformation in temperature or power. whilst new factors are formed, a chemical exchange has handed off, and a chemical reaction has taken place.